Process for production of a high molecular weight ethylene α-olefin elastomer with a metallocene alumoxane catalyst

ABSTRACT

Disclosed is a process for preparing high molecular weight ethylene-α-olefin elastomers, preferably an ethylene-propylene elastomer, by liquid phase polymerization of the requisite monomers in the presence of a metallocene/alumoxane catalyst system. Preferably, the process is carried out as a slurry polymerization utilizing the metallocene/alumoxane catalyst in supported form on a silica gel support with the α-olefin monomer maintained in liquid state and used in excess to serve as a polymerization diluent. The metallocene component of the catalyst by which the process is practiced is of the formula: ##STR1## wherein M is zirconium, titanium or hafnium; each R 1  independently is a C 1  -C 20  linear, branched or cyclic alkyl group or a C 2  -C 4  cyclic alkylene group which forms a fused ring system group; R 2  is a C 1  -C 6  linear, branched or cyclic alkylene, a Si 1  -Si 2  alkyl substituted silanylene group or an alkyl substituted silaalkylene group; each X independently is an alkyl, aryl, halide, hydride or oxygen bridge of a zirconocene dimer; &#34;y&#34; is a number 2, 3 or 4, and &#34;b&#34; is a number 0 or 1. M is preferably zirconium. Most preferably, the supported zirconocene/alumoxane catalyst is prepolymerized with ethylene or another olefin to provide spherical, free-flowing catalyst particles which give free-flowing particulate elastomer product from the slurry polymerization.

This is a division of application Ser. No. 207,819, filed June 16, 1988,now U.S. Pat. No. 4,871,705.

FIELD OF THE INVENTION

This invention relates to a process for preparing high molecular weightethylene-α-olefin elastomers, preferably an ethylene-propyleneelastomer, by liquid phase polymerization of the requisite monomers inthe presence of a zirconium, titanium, or hafnium metallocene/alumoxanecatalyst system. Preferably, the process is carried out as a slurrypolymerization utilizing a zirconocene/alumoxane catalyst in supportedform on a silica gel support with the α-olefin monomer maintained inliquid state and used in excess to serve as a polymerization diluent.Most preferably, the supported zirconocene/alumoxane catalyst isprepolymerized with ethylene or another olefin to provide spherical,free-flowing catalyst particles which give free-flowing particulateelastomer product from the slurry polymerization.

BACKGROUND OF THE INVENTION

As is well known to those skilled in the art, various processes andcatalysts exist for the homopolymerization or copolymerization ofα-olefins. For example, processes are known for polymerizing ethylene orpropylene, either alone or in the presence of small quantities of othermonomers, to produce plastics. These plastics are typically used in suchapplications as blow and injection molding, extrusion coating, film andsheeting, pipe, wire and cable. Also for example, it is well known tocopolymerize ethylene, propylene, and optionally a third monomer such asnon-conjugated dienes, to make elastomers. Ethylene-propylene elastomersfind many end-use applications due to their resistance to weather, goodheat aging properties and their ability to be compounded with largequantities of fillers and plasticizers. Typical automotive uses areradiator and heater hose, vacuum tubing, weather stripping and spongedoorseals. Typical industrial uses are for sponge parts, gaskets andseals.

Due to their different properties and end uses, it is important todistinguish between those factors affecting elastomeric or plasticproperties of α-olefin polymers. While such faCtors are many andcomplex, a major one of instant concern is that related to sequencedistribution of the monomers throughout the polymer chain.

For polyolefin plastics, sequence distribution is of little consequencein determining polymer properties since primarily one monomer is presentin the chain. Accordingly, in plastic copolymers the majority monomerwill be present in the form of long monomeric blocks.

While sequence distribution is thus of little concern with respect topolymeric plastics, it is a critical factor to be considered withrespect to elastomers. If the olefinic monomers tend to form long blockswhich can crystallize, elastic properties of the polymer are poorer thanin a polymer with short monomer sequences in the chain.

For example, titanium catalysts which can produce stereoregularpropylene sequences ar particularly disadvantageous since creatingblocks of either ethylene or propylene will lead to undesirable levelsof crystallinity in an elastomer.

At a given comonomer composition, sequence distribution is primarily afunction of the catalyst components chosen. It can thus be seen that theartisan must exercise extreme care in selecting a catalyst system formaking elastomers, with their critical dependency on sequencedistribution. It can also be seen that, on the other hand, no suchrestrictions apply to the selection of a catalyst system for makingplastic polymer.

To avoid crystallinity in copolymers, it is also necessary to use acatalyst that produces a material with a narrow compositionaldistribution so that fractions containing a high content of one monomerare not present.

Furthermore, when making ethylene-α-olefin copolymers it is well knownthat the α-olefin may act as a chain transfer agent. For essentiallycrystalline copolymers with low α-olefin content, the molecular weightmodifying effect of the α-olefin may be insignificant. However, whenmaking copolymers with compositions in the elastomer range, catalyststhat give high molecular weight plastic copolymers may produce lowmolecular weight polymers unsuitable for elastomer applications. In asimilar fashion, undesirable molecular weight distribution changes canoccur or the compositional distribution can change.

In view of the complicated and poorly understood relationship betweenpolymer composition and catalyst performance, it is difficult for theartisan to predict the behavior of a catalyst for the production of anelastomer if it has only been used previously to make plastic homo- orcopolymers.

European Patent Application 206,794 discloses that certain supportedmetallocene/alumoxane systems, particularly bis(cyclopentadienyl)transition metal metallocenes, in which the cyclopentadienyl ligands areunsubstituted or substituted and may be bridged by an alkylene or asilanylene group, are useful for polymerizing ethylene to a homopolymeror to a copolymer with an α-olefin for purposes of modifying the clarityor impact properties of the polyethylene polymer product.

The art has also indicated that amorphous ethylene-propylene copolymersmay be produced by metallocene/alumoxane catalyst systems in which themetallocene component is a particular species of metallocene. As used inthe art the term "EPC" means a copolymer ethylene and an α-olefin whichexhibits the properties of an elastomer as defined in ASTM D1566 underrubber. However, as heretofore reported, the EPC's so produced have beentoo low in molecular weight to be suitable for use as a commercialelastomeric material, especially when the elastomer has more than 20 wt% incorporated propylene. Also, the activities of the catalysts employedhave been too low for production of products with low residues ofcatalyst in a reasonable time.

In U.S. Pat. No. 4,937,299 of Ewen et al, issued June 26, 1990 it isindicated that an alumoxane system withdimethylsilanylenedicyclopentadienyl zirconium dichloride orbis(cyclopentadienyl) titanium diphenyl will catalyze production of alow molecular weight EPC, and that such catalyst systems may be employedin conjunction with other distinct metallocene/alumoxane catalystsystems to produce reactor blends of an EPC with high densitypolyethylene (HDPE) and linear low density polyethylene (LLDPE) such as,HDPE/EPC, LLDPE/EPC, HDPE/LLDPE/EPC reactor blends or the like. The EPCcomponent of the blends so produced--which by itself by reason of itslow molecular weight is not a commercially useful elastomer--is usefulin the context of a modifier blend component for the base HDPE or LLDPEwith which it is coproduced.

Japanese Kokai numbers 119,215; 121,707; and 121,709 disclose productionof soft copolymers variously of ethylene-α-olefin, propylene-α-olefin,butylene-a-olefin, using a metallocene/alumoxane catalyst system whereinthe metallocene is a metal salt of a lower alkylene bridged-bis(cyclopentadienyl), -bis(indenyl) or -bis(tetrahydroindenyl)compound. The Japanese Kokai represent that copolymer products may beproduced by a gas or liquid phase reaction procedure to have a widerange of properties such as crystallinities from 0.5-60%, while having amolecular weight distribution (MWD) less than 3 with low levels ofboiling methyl acetate soluble components. The Japanese Kokai representthat such copolymerization may be carried out in the presence of suchcatalysts at temperatures from -80° to 50° C. under pressures rangingfrom ambient to 30 kg/cm². Yet in the examples of the first two JapaneseKokai, which illustrate actual production of such materials, thereaction conditions illustrated are temperatures of -10° to -20° C. atreaction times of from 5 to 30 hours using solution polymerization withtoluene as the solvent. A process as illustrated by the operatingexamples of the first two Japanese Kokai is not attractive from astandpoint of commercial production since the long reaction times, lowtemperatures and need to separate polymer product from the reactionsolvent impose severe increases in production cost of the resultingcopolymer material. The process of Japanese Kokai 121,709 is alsounattractive for commercial production due to the use of toluene as asolvent and the expense of separating and recycling the large volume ofsolvent.

A process by which EPC elastomers of commercially acceptable propertiesmay be produced within a range of reaction conditions which are suitablefor commercial practice, using metallocene/alumoxane catalyst systems,has not been demonstrated. For an EPC elastomer to be considered to havecommercially acceptable properties, it should have a Mooney viscosity(ML₁₊₈ at 127° C.) no less than 10, a weight-average molecular weight noless than 110,000, a glass transition temperature below -40° C. and adegree of crystallinity no greater than 25%. For certain applications,e.g. extrusion performance, EPC elastomers should also have a molecularweight distribution characterized by the ratio of weight-average tonumber-average molecular weights of 5 or less. The range of reactionconditions most economical, hence commercially viable for practice,under which EPC elastomers should be produced is a reaction temperatureranging from 0° to 80° C. at reaction residence times of less than 6hours. Desirably, the reaction conditions should minimize or eliminatethe number of extrinsic treatment steps needed to isolate the polymerproduct in final marketable form. Hence, it is desirable for theproduction method to employ as a reaction diluent one or more of themonomers rather than an inert solvent from which the polymer productmust later be separated. It is also desirable that the product beproduced in the form of granules suspended in the reaction medium forease of isolation and subsequent processing. Finally, it is desirablethat the catalyst be sufficiently active that removal of catalystresidue (deashing) from the product is not needed.

SUMMARY OF THE INVENTION

The invention comprises a process employing a metallocene/alumoxanecatalyst system in which the metallocene is a specific class ofzirconocene, titanocene or hafnocene which provides for the productionof high molecular weight ethylene-α-olefin elastomers under reactionconditions suitable for commercial practice. Employment of one of thespecified metallocenes, preferably a zirconocene, in themetallocene/alumoxane catalyst in a slurry reaction process results inthe production of high molecular weight ethylene-α-olefin elastomerswhich typically have a low ash content (where ash refers to the catalystand cocatalyst residue in the polymer), so that deashing is notrequired.

The metallocene component of the metallocene/alumoxane catalyst systememployed in the practice of the process of this invention is of thefollowing formula: ##STR2## wherein M is zirconium, titanium or hafnium;each R¹ independently is a C₁ -C₂₀ linear, branched or cyclic alkylgroup or a C₂ -C₄ cyclic alkylene group which forms a fused ring system;R² is a C₁ -C₆ linear, branched or cyclic alkylene, a Si₁ -Si₂ alkylsubstituted silanylene group or an alkyl substituted silaalkylene group;each X independently as a halide, hydride, oxygen bridge of ametallocene dimer, or a hydrocarbyl radical such as an aryl group or alinear, branched or cyclic alkyl group; "y" is a number 2, 3 or 4, and"b" is a number 0 or 1. Preferably M is zirconium. Typically the Xhydrocarbyl group may have from 1 to 20 carbon atoms, but may be greaterif desired.

A preferred catalyst system is of the following formula: ##STR3##wherein M, X, R¹, R², and "b" are as previously defined and "z" is anumber 0, 1 or 2. The most preferred catalysts are those of formula IIwherein M is zirconium, "b" is 1 and R² is an alkyl substitutedsilanylene group.

Utilizing the defined metallocene in the metallocene/alumoxane catalystwith which the process is practiced, the process may be practiced withthe catalyst in non-supported form by adding the metallocene andalumoxane in hydrocarbon solutions to the polymerization diluent.Preferably, the metallocene/alumoxane catalyst system is used in aheterogeneous form on a catalyst support, such as a silica gel support,and polymerization is carried out by a slurry polymerization techniquein which an α-olefin monomer suitable for use as a polymerizationdiluent is used in excess and maintained in the liquid state. By"slurry" polymerization it is meant that the product polymer is producedin the form of granules suspended in the polymerization diluent. Morepreferably, the supported metallocene/alumoxane catalyst isprepolymerized with ethylene or an α-olefin to control EPC granule sizeand size distribution for the direct production of granular EPC productsfrom the slurry process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention relates to a process for producing in high yieldethylene-α-olefin elastomers of high molecular weight, lowcrystallinity, and low ash. In particular, it relates to a catalystsystem comprising metallocene/alumoxane systems which are highly activefor the production of high molecular weight ethylene-α-olefin elastomersin a slurry polymerization process.

As used herein the term "EPC" means a copolymer of ethylene and anα-olefin which exhibits the properties of an elastomer. The α-olefinssuitable for use in the preparation of elastomers with ethylene arepreferably C₃ -C₁₆ α-olefins. Illustrative non-limiting examples of suchα-olefins are propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and1-dodecene. If desired, more than one α-olefin may be incorporated.

The EPC elastomers may contain about 20 up to about 90 weight percentethylene, more preferably about 30 to 85 weight percent ethylene, andmost preferably about 35 to about 80 weight percent ethylene.

The catalyst employed in the method of this invention is ametallocene/alumoxane system wherein the metallocene component of thecatalyst system is of the formula: ##STR4## wherein M is zirconium,titanium or hafnium; the R² bridging group, if present, is a linear,branched or cyclic alkylene group having from one to six carbon atoms,an akyl substituted silaalkylene group having from one to two siliconatoms in place of carbon atoms in the bridge, or a Si₁ -Si₂ alkylsubstituted silanylene group; each R¹ independently is a linear orbranched hydrocarbyl radical having from one to twenty carbon atoms or acyclic hydrocarbylene di-radical having carbon atoms joined to differentring positions of the cyclopentadienyl group to form a C₄ -C₆ fused ringsystem; each X independently is a hydride, halide, oxygen bridge of ametallocene dimer, or a hydrocarbyl radical such as an aryl group or alinear, branched or cyclic alkyl group; "y" is a number from 2 to 4 and"b" is a number 0 or 1. The metallocene is preferably a zirconocene,that is M is zirconium. Exemplary R¹ hydrocarbyl radicals are methyl,ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl,nonyl, decyl, cetyl, 2-ethylhexyl, phenyl, and the like. Exemplary R¹hydrocarbylene di-radicals are ethylene, propylene, butylene or thelike. Preferably the R¹ group is a cyclic hydrocarbylene of butylenewhich is joined to adjacent ring positions of the cyclopentadiene toprovide a tetrahydroindenyl fused ring structure. Hence, in thepreferred case the metallocene component of the catalyst system is azirconocene of the formula: ##STR5## wherein R¹ is a linear or branchedhydrocarbyl radical having from 1 to 20 carbon atoms; "z" is an integernumber from 0 to 2; and R², X and "b" are as previously described.Exemplary R² linear alkylene radicals are methylene, ethylene,propylene, butylene, pentylene, hexylene and the like. Exemplary R²cyclic alkylene diradicals are cyclobutylene, cyclopentylene,cyclohexylene and the like. Exemplary R² alkyl substituted silanylenegroups are dimethylsilanylene, methylethyl silanylene,diethylsilanylene, tetramethyldisilanylene, tetraethyldisilanylene, andthe like. The R² group may also be an alkyl substituted silaalkylenegroup, i.e. a bridge composed of a carbon-silicon sequence, e.g.--Si(R')₂ --C(R")₂ -- wherein R' is lower alkyl and R" is hydrogen orlower alkyl. Exemplary R² alkyl substituted silaalkylene groups are1-sila-1,1-dimethylethylene, 2-sila-2,2-dimethylpropylene,1,3-disila-1,1,3,3-tetramethyl propylene and the like. Preferably R² isethylene, dimethylsilanylene or "b" is 0 and R² is absent, mostpreferably R² is dimethylsilanylene.

The preferred zirconocenes contain bis(tetrahydroindenyl),ethylene-bis(tetrahydroindenyl) anddimethylsilanylene-bis(tetrahydroindenyl) ligands, withdimethylsilanylene-bis(tetrahydroindenyl) zirconocenes the mostpreferred. Exemplary of suitable zirconocenes are bis(tetrahydroindenyl)zirconium dichloride, ethylene bridged bis(tetrahydroindenyl) zirconiumdichloride, and dimethylsilanylene bridged bis(tetrahydroindenyl)zirconium dichloride.

Methods for preparing the required- metallocene component are known inthe art, for example see H. H. Brintzinger,et al.; Journal ofOrganometallic Chemistry, Vol. 288, p. 63 ( 1985); C. S. Ba]qur, W. R.Tikkanen, J. L. Petersen; Inorg. Chem., Vol. 24, pp. 2539-2546 (1985).

The alumoxane component of the catalyst system is an oligomeric aluminumcompound represented by the general formula (R-Al-O)_(n), which is acyclic compound, or R(R-Al-O)_(n) AlR₂, which is a linear compound. Inthe general alumoxane formula R is a C₁ -C₅ alkyl radical, for example,methyl, ethyl, propyl, butyl or pentyl and "n" is an integer from 1 toabout 50. Most preferably, R is methyl and "n" is at least 4. Alumoxanescan be prepared by various procedures known in the art. For example, analuminum alkyl may be treated with water dissolved in an inert organicsolvent, or it may be contacted with a hydrated salt, such as hydratedcopper sulfate suspended in an inert organic solvent, to yield analumoxane. Generally, however prepared, the reaction of an aluminumalkyl with a limited amount of water yields a mixture of the linear andcyclic species of the alumoxane.

The catalyst employed in the method of the invention is formed uponadmixture of a metallocene, preferably a zirconocene, as specified, withan alumoxane. The catalyst system may be prepared as a non-supportedcatalyst by mixing the requisite metallocene and alumoxane in a suitablediluent either in the presence or absence of monomers. Thepolymerization employing non-supported catalysts can be carried outeither by solution or slurry polymerization procedures. In the contextof the present invention the catalyst system is preferably prepared andemployed as a heterogeneous catalyst by adsorbing the requisitemetallocene and alumoxane components on a catalyst support material suchas silica gel, alumina or other suitable inorganic support material.

The heterogeneous form of catalyst system is particularly suitable for aslurry polymerization procedure. For the production of EPC elastomers inaccordance with the method of this invention, it is preferred to utilizethe α-olefin monomers in liquified state as the polymerization diluent.As a practical limitation, slurry polymerization takes place in liquiddiluents in which the polymer product is substantially insoluble.Preferably, the diluent for a slurry polymerization is one or morehydrocarbons with less than 5 carbon atoms. If desired, saturatedhydrocarbons such as ethane, propane, or butane may be used in whole orpart as the diluent. Likewise, the α-olefin monomer or a mixture ofdifferent α-olefin monomers may be used in whole or part as the diluent.Most preferably the diluent comprises in major part the α-olefin monomeror monomers to be polymerized.

The support material for preparing a heterogeneous catalyst may be anyfinely divided inorganic solid porous support, such as talc, silica,alumina, silica-alumina or mixtures thereof. Other inorganic oxides thatmay be employed either alone or in combination with silica orsilica-alumina are magnesia, titania, zirconia, and the like. Theinorganic oxides should be dehydrated, as is well known in the art, toremove water. If desired, the residual surface hydroxyl groups in theinorganic solid porous support may be removed by additional heating orby reaction with dehydroxylating agents such as lithium alkyls, silylchlorides, aluminum alkyls, or preferably with alumoxane. A preferredcatalyst support is a dehydrated inorganic oxide treated with analumoxane, more preferably methylalumoxane. A suitable support materialis a dehydrated silica gel treated with methylalumoxane.

The normally hydrocarbon soluble metallocene and alumoxane are preparedas a heterogeneous supported catalyst by deposition on a supportmaterial, such as a dehydrated silica gel treated with methylalumoxane.A suitable silica gel would have a particle diameter in the range 1-600microns, preferably 10-100 microns; a surface area of 50-1000 m² /g,preferably 100-500 m² /g; and a pore volume of 0.5-3.5 cm³ /g. Thesilica gel may be heat treated at 100°-1000° C., preferably 300°-800° C.for a period of 1-100 hours, preferably 3-24 hours, to insure its use indehydrated form.

The catalyst system obtained through contacting of the metallocene andthe alumoxane cocatalyst may be formed prior to introduction of thesecomponents into the reactor, or, alternatively, it may be formed in thereactor. In the case wherein a zirconocene is employed and the activesystem is formed in the reactor, the mole ratio of Al to Zr in thereactor is desirably in the range 10-5000, preferably 20-4000 and mostpreferably 20-1000. In the case that the active system is formed outsidethe reactor, the preferred ratio of Al to Zr is in the ran9e 1-200,desirably 20-200. In this case, additional alumoxane cocatalyst may beused in the reactor so that the total ratio of Al to Zr is in the range10-5000, preferably 20-4000 and most preferably 20-1000. Likewise, inthis case, a small amount of another alkylaluminum compound, such astriethylaluminum or trisobutylaluminum, may be added to the reactortogether with, or instead of, additional alumoxane, for the purposes ofscavenging any impurities which may be present in the reactor. In all ofthe above, the catalyst or cocatalyst may be contacted in the reactorwith one of the components present on a suitable support, as describedbelow.

As stated before, zirconocenes of the specified cases are the preferredmetallocenes. Consequently further discussion of the catalyst will bewith specific reference to zirconocenes although it should be understoodthat similar conditions and procedures are applicable to titanocenes andhafnocenes as well.

In the preferred case a dehydrated silica gel is contacted withalumoxane and subsequently with the zirconocene. If desired thezirconocene can be added to a dehydroxylated support material prior tocontacting the support material with an alumoxane. In accordance withthe preferred embodiment of this invention, the alumoxane dissolved in asuitable inert hydrocarbon solvent is added to the support materialeither dry or slurried in the same or other suitable hydrocarbon liquidand thereafter the zirconocene is added to the slurry, preferably afterdrying the support under vacuum and reslurrying in a light hydrocarbon.The zirconocene is added to the slurry in an amount sufficient toprovide from about 0.02 to about 5.0 weight percent zirconium metalbased on total catalyst weight. The zirconocene is more preferably addedin an amount to provide from about 0.10 to about 1.0 weight percentzirconium metal based on total catalyst weight.

The treatment of the support material, as mentioned above, is conductedin an inert solvent. The same inert solvent or a different inert solventis also employed to dissolve the zirconocene and alumoxanes. Preferredsolvents include the various hydrocarbons which are liquid at treatmenttemperatures and pressures and in which the individual ingredients aresoluble. Illustrative examples of useful solvents include the alkanessuch as propane, butane, pentane, iso-pentane, hexanes, heptanes,octanes and nonanes; cycloalkanes such as cyclopentane and cyclohexane;and aromatics such as benzene, toluene, xylenes, ethylbenzene anddiethylbenzene. Sufficient solvent should be employed so as to provideadequate heat transfer away from the catalyst components during reactionand to permit good mixing.

The temperature maintained during the contact of the reactants can varywidely, such as, for example, from 0° to 100° C. Greater or lessertemperatures can also be employed. The reaction between the alumoxaneand the support material is rapid, however, it is desirable that thealumoxane be contacted with the support material for about one half hourup to eighteen hours or greater. Preferably, the reaction is maintainedfor about one hour at 25°-100° C.

At all times, the individual ingredients as well as the recoveredcatalyst components must be protected from oxygen and moisture.Therefore, the reactions are performed in an oxygen and moisture freeatmosphere and the catalyst is recovered in an oxygen and moisture freeatmosphere. Preferably, therefore, the reactions are performed in thepresence of an inert dry gas such as, for example, nitrogen. Therecovered solid catalyst is maintained in the inert gas atmosphere.

Upon completion of the deposition of the zirconocene and alumoxane onthe support, the solid material can preferably be treated with a smallamount of monomer, e.g. ethylene, to form an amount of polymer on thesolid catalyst materials to increase the catalyst weight at least 50%,desirably from about 100 to about 500% based on the total weight ofcatalyst and support material. Such treatment is hereafter referred toas prepolymerization of the catalyst. Then the solid material, as suchor as prepolymerized, can be recovered by any well-known technique. Forexample, the solid catalyst material can be recovered from the liquid byfiltration, by vacuum evaporation, or by decantation. The solid isthereafter dried under a stream of pure dry nitrogen or dried undervacuum.

Prepolymerization of the solid catalyst material aids in obtaining anEPC elastomer produced therefrom during slurry polymerization inwell-defined particle form. The prepolymerized catalyst may be rinsedwith a hydrocarbon to provide the good granular particle form.Prepolymerization also greatly reduces the requirement for alumoxane.For example, an Al:Zr ratio of 1000:1 or greater foralumoxane:zirconocene is needed for high activity when the alumoxane isadded to the liquid phase of the reactor, but a ratio less than 100:1 issufficient when the alumoxane is incorporated into the prepolymerizedcatalyst. For a prepolymerized catalyst the ratio of aluminum tozirconium may range from about 1:1 to 500:1, preferably from about 20:1lo 100:1, and high activities will still be obtained.

Most preferably, the supported catalyst is prepared in the followingmanner (1) forming a slurry by the addition of the alumoxane dissolvedin a suitable solvent, toluene for example, to the support; (2) stirringthe slurry at 60°-80° C. for 30-60 minutes; (3) removal of solvent undervacuum with heating sufficient to produce a dry powder; (4) adding alight hydrocarbon, pentane for example, to slurry the powder; (5) addinga solution of the zirconocene in pentane or a minimum amount of tolueneand stirring for 15-60 minutes at 20°-60° C.; (6) prepolymerizing withethylene or other olefin in the pentane slurry and then collecting,rinsing and drying the catalyst. For best particle form, it is preferredto add no alumoxane to the reactor beyond what is on the prepolymerizedcatalyst. Sufficient aluminum alkyl, such as triethylaluminum ortriisobutylaluminum, to scavenge impurities in the feeds may be added,but not an excess.

In accordance with the preferred procedure of this invention an EPCelastomer is produced by slurry polymerization utilizing the α-olefinmonomer or mixture of monomers as the polymerization diluent in which asupported zirconocene/alumoxane catalyst system is suspended. Ethyleneis added to the reaction vessel in an amount sufficient to produce thedesired ethylene content in the EPC product. The differential pressureof ethylene, in excess of the vapor pressure of the α-olefin monomer,required to produce a given ethylene content depends on the structure ofthe zirconocene used. Generally the polymerization process is carriedout at an ethylene differential pressure of from about 10 to about 1000psi, most preferably from about 40 to about 600 psi; and thepolymerization diluent is maintained at a temperature of from about -10°to about 100° C.; preferably from about 10° to about 70° C., and mostpreferably from about 20° to about 60° C. Under the conditions as aboveindicated the ethylene and α-olefin monomers copolymerize to an EPCelastomer.

The polymerization may be carried out as a batchwise slurrypolymerization or as a continuous slurry polymerization. The procedureof continuous process slurry polymerization is preferred, in which eventethylene, liquid α-olefin, and catalyst are continuously supplied to thereaction zone in amounts equal to the EPC polymer, ethylene, α-olefin,and catalyst removed from the reaction zone in the product stream.

Without limiting in any way the scope of the invention, one means forcarrying out the process of the present invention is as follows: In astirred-tank reactor liquid propylene either into the vapor phase of thereactor, or sparged into the liquid phase as well known in the art. Thereactor contains a liquid phase composed substantially of liquidpropylene together with dissolved ethylene gas, and a vapor phasecontaining vapors of all monomers. Catalyst and cocatalyst (and/orscavenger aluminum alkyl) are introduced via nozzles in either the vaporor liquid phase. The reactor temperature and pressure may be controlledvia reflux of vaporizing α-olefin monomer (autorefrigeration), as wellas by cooling coils, jackets etc. The polymerization rate is controlledby the rate of catalyst addition, or by the concentration of cocatalystmanipulated separately. The ethylene content of the polymer product isdetermined by the zirconocene used and by the ratio of ethylene topropylene in the reactor, which is controlled by manipulating therelative feed rates of these components to the reactor.

As shown in Table I, for a given set of reaction conditions,zirconocenes with more open reaction sites incorporate propylene moreeasily than those with more hindered sites. Reaction sites become moreopen with shorter bridges between the cyclopentadienyl rings and morehindered by addition of bulkier substituents to the rings. To open thereaction site, even where a bulky substituent is carried by thecyclopentadienyl rings, it is preferred to employ a short bridge betweenthe rings, such as a dimethylsilanylene bridge. However, for anyzirconocene the incorporation can be varied by adjustment of theethylene/propylene ratio in the reactor.

The polymer product molecular weight is controlled, optionally, bycontrolling other polymerization variables such as the temperature, orby a stream of hydrogen introduced to the gas phase of the reactor, asis well known in the art. The polymer product which leaves the reactoris recovered by flashing off gaseous ethylene and propylene at reducedpressure, and, if necessary, conducting further devolatilization inequipment such as a devolatilizing extruder. In a continuous process theresidence time of the catalyst in the reactor generally is from about 20minutes to 8 hours, preferably 30 minutes to 6 hours, and morepreferably 30 minutes to 4 hours.

The final properties of the EPC elastomer produced by the process of theinvention are related to the zirconocene structure and the reactionconditions, particularly the ethylene/propylene ratio and reactiontemperature.

The various zirconocenes in Table I exhibit different activities for agiven set of reaction conditions. Naturally, higher activity catalystsare preferred provided that the catalyst can produce the desired polymerproperties. However, less active catalysts may be preferred for theirspecific incorporation characteristics. For instance, to reduce totalreactor pressure while making high ethylene content EPC, an unbridged orlong bridged zirconocene may be preferred. These catalysts are very longlived, so longer reaction times will result in a higher yield of an EPCelastomer for a given catalyst concentration, providing a product withlow catalyst residues.

In the Examples which illustrate the practice of the invention theanalytical techniques described below were employed for the analysis ofthe resulting EPC elastomer products The Mooney viscosity, ML₁₊₈, 127°C., was measured in a Monsanto Mooney Viscometer according to ASTMD1646. Polymer ethylene content was determined by infrared analysisaccording to ASTM D3900. Molecular weight determinations for EPCelastomer products were made by gel permeation chromatography (GPC)according to the following technique. Molecular weights and molecularweight distributions were measured using a Waters 150 gel permeationchromatograph equipped with a differential refractive index (DRI)detector and a Chromatix KMX-6 on-line light scattering photometer. Thesystem was used at 135° C. with 1,2,4-trichlorobenzene as the mobilephase. Shodex (Showa Denko America, Inc.) polystyrene gel columns 802,803, 804 and 805 were used. This technique is discussed in "LiquidChromatography of Polymers and Related Materials III", J. Cazes editor,Marcel Dekker, 1981, p. 207 which is incorporated herein by reference.No corrections for column spreading were employed; however, data ongenerally accepted standards, e.g. National Bureau of StandardsPolyethlene 1484 and anionically produced hydrogenated polyisoprenes (analternating ethylene-propylene copolymer) demonstrated that suchcorrections on Mw/Mn were less than 0.05 units. Mw/Mn was calculatedfrom an elution time. The numerical analyses were performed using thecommercially available Beckman/CIS customized LALLS software inconjunction with the standard Gel Permeation package, run on aHewlett-Packard 1000 computer.

CATALYST PREPARATION EXAMPLES Example 1 Synthesis ofmethylalumoxane/silica gel support [MAO/SiO₂ ].

In a dry box, 30 ml of a solution of methylalumoxane (MAO) in toluene(supplied by Ethyl Corporation under label identification as 1M inaluminum) was added to 15 g of Davison 955 silica gel which had beendried at 800° C. for 4 hours. The solvent was removed under vacuum.

Example 2 Silica supported bis(tetrahydroindenyl)zirconium dichloridecatalyst

A MAO-treated silica gel was prepared in the same manner as in Example1, except that 25 ml of MAO (Ethyl Corporation, 1M in aluminum) wasadded instead of 30 ml. 5 g of the resulting MAO-treated silica gel wasweighed into a 50 ml Schlenk flask equipped with a magnetic stir bar ina dry box. 250 mg of bis(tetrahydroindenyl)zirconium dichloride wasadded to 7 ml of toluene, and the toluene solution was added dropwise tothe MAO-treated silica gel support with magnetic stirring over 30minutes. The solid caked. After 5 minutes of homogenization using a stirbar, 6 ml of additional dry toluene was added to slurry the silica. Theflask was removed from the dry box to a vacuum line and toluene wasremoved under vacuum. The dried solids nominally contain 4.8% by weightof the catalyst system or 1.1 wt % Zr.

Example 3 Silica supported ethylene bridged bis(tetrahydroindenyl)zirconium dichloride catalyst.

In a dry box, 2.0 g of the MAO-treated silica gel support made inExample 1 was weighed into a 50 ml Schlenk flask equipped with a 1 inchmagnetic stir bar. 50 mg of ethylene-bis(tetrahydroindenyl)zirconiumdichloride was dissolved in 3 ml of toluene with the aid of a heat gun.After dissolution, the solution was added dropwise to the 2 g ofMAO-treated silica gel and then 4 ml of additional dry toluene was addedto convert the powder into a slurry. This was removed from the dry boxand stirred at 55° C. in an oil bath for 30 minutes. The slurry was thenevacuated on a Schlenk line. When completely dry, 1.834 g of solids wererecovered with a nominal loading of 2.4 wt % zirconocene or 0.52 wt %Zr.

Example 4 Silica supported dimethylsilanylene-bis(tetrahydroindenyl)zirconium dichloride catalyst

In a dry box, a solution of 50 mg of dimethylsilanylenebis(tetrahydroindenyl)zirconium dichloride in 3 ml of toluene was addeddropwise to 2.0 g of the MAO-treated silica gel of Example 1 which wasvigorously stirred with a magnetic stir bar. Another 4 ml of toluene wasthen added to slurry the solids. The slurry was stirred at 55° C. for 30minutes and then the solvent was removed under vacuum. The catalyst isnominally 2.4 wt % zirconocene or 0.49 wt % Zr.

Example 5 Synthesis of Prepolymerized Catalyst For Run C3 of Example 9

To 5 g of Davison 948 silica gel (dried at 800° C. for 4 hours) in a 500ml flask equipped with a magnetic stir bar, was added 85 ml of MAO intoluene (Ethyl Corporation, reported 1M in aluminum). The toluene wasremoved under vacuum, with heating to 45° C. To 1.08 g of the solidresidue (which had been rinsed with 10 ml, then 4 ml of dry pentane,filtering after each rinse), magnetically stirred in 25 ml of drypentane, was added 11 mg of bis(tetrahydroindenyl)zirconium dichloridedissolved in 25 ml of dry pentane. The slurry was then stirred at roomtemperature for one hour.

With water bath cooling of the reaction flask, ethylene was added at 4mmol/min for 30 min. The powder was collected and dried on a frittedglass funnel in a dry box. 4.37 g of prepolymerized catalyst wascollected as a tan powder with several larger pieces of polymer from theflask walls. The catalyst was nominally 19 wt % silica, 5.7 wt %methylalumoxane, 0.25 wt % zirconocene (0.057% Zr), and 75 wt %polyethylene. Since the supported catalyst is only 25 wt % of theprepolymerized catalyst, this is labeled PP(400)THIZ in Table III,indicating that the catalyst was prepolymerized to 400% of its originalweight and contained the tetrahydroindenyl zirconocene (THIZ).

Example 6 Synthesis of Prepolymerized Catalyst for Run C8 of Example 9

To 240 g of Davison 948 silica gel (dried at 800° C.) in a 2 gallonreactor equipped- with a mechanical stirrer, was added 2500 ml ofmethylalumoxane in toluene (5.5 wt % Al). The toluene was removed withsparging nitrogen while heating to 80° C. The reactor was cooled to 25°C. and the powder rinsed twice with 2 liters of dry isopentane,decanting to the top of the settled slurry after each rinse. Four litersof isopentane was then added to slurry the powder, and a solution of 5.0g of bis(tetrahydroindenyl)zirconium dichloride in 300 ml of toluene wasadded over 10 minutes with vigorous stirring. Ethylene was added to thestirring slurry for 1.5 hours while the temperature was controlled tobelow 30° C. The slurry was allowed to settle and was transferred to thedry box where it was dried on a filter and stored under nitrogen. 941 gof tan powder was collected which was nominally 24 wt % silica, 6.9 wt %methylalumoxane, 0.50 wt % zirconocene (0.12 wt % Zr), and 67 wt %polyethylene. Since the supported catalyst is only 33 wt % of theprepolymerized catalyst, this is labeled PP(300)THIZ in Table III,indicating that the catalyst was prepolymerized to 300% of its originalweight and contained the tetrahydroindenyl zirconocene.

Example 7 Synthesis of Prepolymerized Catalyst for Run C11 of Example 10

To 10 g of Davison 948 silica gel (dried at 800° C. for 4 hours) in a500 ml flask equipped with a magnetic stir bar, was added 200 ml of MAOin toluene (from Ethyl Corporation, reported 1M in aluminum). Thetoluene was removed under vacuum, after heating at 80° C. for 1 hour. To2 g of the solid residue, magnetically stirred under nitrogen in 35 mlof dry pentane, was added 40 mg ofdimethylsilanylene-bis(tetrahydroindenyl)zirconium dichloride (STHI)dissolved in 3 ml of dry toluene. The slurry was then stirred at roomtemperature for 15 minutes.

With water bath cooling of the reaction flask, ethylene was added at 6mmol/min. for 30 minutes. The powder was then collected on a frittedglass funnel in the dry box, washed three times with 30 ml of drypentane, and dried. Collected was 6.17 g of prepolymerized catalyst as atan powder with several larger pieces of polymer from the flask walls.The catalyst was nominally 12 wt % methylalumoxane, 0.65 wt %zirconocene (0.13 wt % Zr), and 67 wt % polyethylene. Since the catalystwas prepolymerized to 308% of its original weight, this is labeledPP(308)STHI in Table III.

POLYMERIZATION EXAMPLES Example 8 Standard Nonsupported CatalystPolymerization: Procedure A

A clean, dry one liter autoclave was flushed with propylene and ameasured quantity of MAO in toluene (Ethyl Corporation, reported as 1Min aluminum) was added by syringe. The reactor was then charged with 500ml of liquid propylene and brought to the temperature for reaction,where the pressure in the autoclave was measured. The pressure in thereactor was then increased by a measured incremental pressure byaddition of ethylene. To start the run, a measured quantity of thezirconocene dissolved in 3 ml of toluene was injected into theautoclave. Ethylene was supplied to maintain the initial total pressurein the autoclave. After reaction for the desired length of time, themonomers were flashed off, and the temperature brought to 25° C. Thepolymer product was recovered from the reactor and dried in a vacuumoven at 50° C. overnight. Amounts and types of catalysts used and theresults of the polymerizations are reported in Table I

Example 9 Standard Supported Catalyst Polymerization: Procedure B

The same procedure of Example 8 was followed except that the supportedcatalyst was injected as a slurry in 3 ml of hexane. Catalystcompositions, quantities of catalyst and of cocatalyst, temperatures andethylene pressures for the runs are given in Table 11.

Example 10 Standard Prepolymerized Catalyst Polymerization: Procedure C

The same procedure of Example 9 was followed, except that no alumoxanecocatalyst was used. Instead, TEAL was used as a scavenger for thepolymerization, and the alumoxane incorporated in the prepolymerizedcatalyst provided the only cocatalyst. Details of the examples usingprepolymerized catalysts are given in Table III.

Table I illustrates the effects of zirconocene structure on activity andproduct properties for a series of runs under similar conditions. Activecatalysts cause strong exotherms at the initiation of the reaction. Thepolymer products invariably foul the reactor internal surfaces whenusing nonsupported catalysts. The combination of fouling and initialexotherm makes these runs difficult to control, causes broadening of themolecular weight distribution, lowers the molecular weight of theproducts, and makes reproducibility difficult.

Nonetheless, the runs in Table I show that most of the zirconocenes withstructures according to the invention (A10-A16) are more active andprovide higher molecular weight products than runs with the comparativecatalysts (A1-A9). The apparent exceptions are with the comparativecatalyst of runs A7 to A9, which is not in accord with the structuresclaimed, but still provided good molecular weight product at areasonable activity in run A7. However, this molecular weight isobtained only at the expense of very high ethylene contents. At lowerethylene content, this catalyst gave lower molecular weights as shown byruns A8 and A9. The catalysts used in runs A11-A14 are clearly the mostactive and provide high molecular weight elastomers over a broad rangeof ethylene content.

Runs A14-A16 show that replacement of chloride by phenyl,trimethylsilylmethyl or an oxygen bridge to a second zirconocene haslittle effect on the activity or molecular weight of the products.

Table II compares the behavior of supported catalysts prepared from twoof the most active zirconocenes of this invention with that of acatalyst prepared from one of the best comparative zirconocenes. Thecomparative catalyst employed in runs B1-B3 show that high activity andhigh molecular weight are not simultaneously obtained; this isespecially true for lower ethylene contents. The comparative catalyst ofruns B1-B3 gave much lower molecular weight products at lower than 70 wt% ethylene. This problem is eliminated with the catalysts of thisinvention. Although good quality EPC may be obtained with the catalystsemployed in this invention even in the absence of additional alumoxaneadded to the slurry (run B11), the activity is dramatically lower. Toobtain high activity, it was required to add additional MAO. In all ofthese runs, the products fouled the reactor as did the nonsupportedcatalysts. Broader MWDs are also noted where initiation exotherms causehigh temperatures. Although the activity of the supported catalysts issomewhat reduced on a g-Zr basis from that of the nonsupportedcatalysts, the activity on a g-cat basis is well above the 1000g/g-cat/h desirable for a commercial process.

Table III illustrates the improved performance obtained with theprepolymerized form of the supported catalysts. For these catalysts, theinitiation exotherm was virtually undetectable in spite of the excellenthigh activities obtained. Furthermore, in contrast to the foulinginvariably obtained with the catalysts in Tables I and II, thesecatalysts did not foul the reactor, and in most cases the particulateproduct was comprised of individual spherical particles of polymer. Thisis a significant advantage for slurry polymerization with this type ofcatalyst.

                                      TABLE I    __________________________________________________________________________    Propylene Slurry Polymerizations Using Unsupported Catalysts (Example 8)                      Exotherm                            Yield                                Activity                                      Ethylene                                           Mw      ML    Run    Zirconocene                      °C.                            g   Kg/g-Zr/h                                      wt % 10.sup.3                                               MWD 1 + 8, 127°    __________________________________________________________________________                                                   C.    Comparative    examples:    A1     Me.sub.2 C(Cp).sub.2 ZrCl.sub.2                      1     7   105   70   172 --  --    A2     Me.sub.2 Si(Cp).sub.2 ZrCl.sub.2                      1     18  281   38   37  --  --    A3     (BenzylCp).sub.2 ZrCl.sub.2                      1     12  254   66   113 --  --    A4     Me.sub.2 Si(MeCp).sub.2 ZrCl.sub.2                      1     33  553   44   72  --  --    A5     Et(Ind).sub.2 ZrCl.sub.2                      13    36  668   41   49  2.3 --    A6     Me.sub.2 Si(Ind).sub.2 ZrCl.sub.2                      15    36  707   36   51  2.7 --    A7     (n-BuCp).sub.2 ZrCl.sub.2                      10    64  1137  83   249 2.6 67    A8.sup.a           (n-BuCp).sub.2 ZrCl.sub.2                      1     29  656   68   126 2.0 17    A9.sup.b           (n-BuCp).sub.2 ZrCl.sub.2                      1     36  322   54   66  2.5 --    Invention    examples:    A10    (n-BuTHI).sub.2 ZrCl.sub.2                      4     59  1330  79   209 2.9 61    A11.sup.c           (THI).sub.2 ZrCl.sub.2                      12    47  3300  83   390 3.6 54    A12.sup.d           Et(THI).sub.2 ZrCl.sub.2                      24    73  2740  50   281 3.4 86    A13    Me.sub.2 Si(THI).sub.2 ZrCl.sub.2                      16    113 2260  40   265 10.6                                                   52    A14    (THI).sub.2 ZrPh.sub.2                      25    116 2460  76   218 7.3 73    A15    (THI).sub.2 Zr(TMSM).sub.2                      8     80  1770  84   --  --  --    A16    [(THI).sub.2 ZrCl].sub.2 O                      20    103 1690  75   --  --  --    __________________________________________________________________________     NOTE: unless otherwise specified, used 0.5 mg zirconocene, 4 mL of     methylalumoxane (1 M in Al), 50° C., 500 mL propylene, 150 psi     differential pressure of ethylene, 30 min run.     .sup.a Used 0.4 mg zirconocene, 8 mL of Methylalumoxane (0.8 M in Al), 10     psi of ethylene.     .sup.b Used 4 mL of methylalumoxane (0.8 M in Al), 50 psi of ethylene, 60     minute run.     .sup.c Used 0.13 mg zirconocene.     .sup.d Used 0.25 mg zirconocene and 2 mL of methylalumoxane.

                                      TABLE II    __________________________________________________________________________    Propylene Slurry Polymerizations Using Supported Catalysts (Example    __________________________________________________________________________    9)                     Catalyst MAO C.sub.2                                      T  ΔT                                            Yield    Run    Zirconocene                     Zirc                        MAO mg                              ml  psi °C.                                         °C.                                            g    __________________________________________________________________________    Comparative    examples:    B1     (n-BuCp).sub.2 ZrCl.sub.2                     2.3%                        7%  20                              6   100 50 1  14    B2     (n-BuCp).sub.2 ZrCl.sub.2                     2.3%                        7%  20                              6   125 65 0  13    B3     (n-BuCp).sub.2 ZrCl.sub.2                     2.3%                        7%  20                              6   125 35 1  6    Invention    examples:    B4     (THI).sub.2 ZrCl.sub.2                     4.8%                        11% 10                              1   150 50 14 56    B5     (THI).sub.2 ZrCl.sub.2                     4.8%                        11% 10                              1   150 35 16 39    B6     (THI).sub.2 ZrCl.sub.2                     4.8%                        11% 10                              1   80  50 10 77    B7     (THI).sub.2 ZrCl.sub.2                     4.8%                        9%  10                              5   100 50 14 111    B8     (THI).sub.2 ZrCl.sub.2                     4.8%                        9%  10                              2   100 50 10 83    B9     (THI).sub.2 ZrPh.sub.2                     4.2%                        16% 5 1   150 50 2  22    B10    (THI).sub.2 ZrPh.sub.2                     4.2%                        16% 5 1   100 50 2  25    B11    (THI).sub.2 ZrPh.sub.2                     4.2%                        16% 50                              a   150 50 1  27    B12    (THI).sub.2 ZrPh.sub.2                     4.2%                        16% 5 2   100 50 1  19    B13    Et(THI).sub.2 ZrCl.sub.2                     2.4%                        11% 50                              1   150 50 16 98    B14    Me.sub.2 Si(THI).sub.2 ZrCl.sub.2                     2.4%                        11% 50                              1   150 50 10 56    B15    Me.sub.2 Si(THI).sub.2 ZrCl.sub.2                     2.4%                        11% 10                              1   150 50 1  20    B16    Me.sub.2 Si(THI).sub.2 ZrCl.sub.2                     2.4%                        11% 10                              b   250 50 1  19    B17    Me.sub.2 Si(THI).sub.2 ZrCl.sub.2                     2.4%                        11% 10                              b   250 40 1  19    __________________________________________________________________________           Activity                  Activity                         C.sub.2                              M.sub.w  ML    Run    Kg/g-Zr/h                  Kg/g-cat/h                         wt % 10.sup.3                                  MWD  1 + 8, 127° C.    __________________________________________________________________________    Comparative    examples:    B1     240    1.4    71   125 2.1  --    B2     220    1.3    74   99  2.4  --    B3     100    0.6    84   351 2.4  --    Invention    examples:    B4     1020   11.1   76   --  --   52    B5     710    7.8    80   700 6.4  no melt    B6     1410   15.4   63   161 6.0  40    B7     2030   22.2   58   182 7.0  27    B8     1520   16.6   69   --  --   37    B9     1120   8.9    83   --  --   --    B10    1250   9.9    76   224 2.8  --    B11    140    1.1    79   318 3.2  98    B12    930    7.4    72   193 3.2  --    B13    760    3.9    61   456 5.3  109    B14    240    2.4    46   315 3.8  83    B15    400    4.0    45   --  --   --    B16    380    3.8    57   255 2.3  --    B17    380    3.8    60   388 2.5  --    __________________________________________________________________________     NOTE: used 500 mL propylene, 30 min run.     a. Used 0.3 mL of 25% TEAL in hexane.     b. Used 1 mL of methylalumoxane and 1 mL of 25% TEAL in hexane.

                                      TABLE III    __________________________________________________________________________    Propylene Slurry Polymerization Using Prepolymerized Catalysts (Example    10)                         25%              Activity                                               Activity        ML              Catalyst   TEAL                             C.sub.2                                T  ΔT                                      Yield                                          Kg/g-                                               Kg/g-                                                    C.sub.2                                                        M.sub.w                                                               1 + 8,    Run       Catalyst              Zirc                  MAO mg ml  psi                                °C.                                   °C.                                      g   Zr/h cat/h                                                    wt %                                                        10.sup.3                                                           MWD 127°    __________________________________________________________________________                                                               C.    C1 PP(200)THIZ              0.60%                  13% 195                         0.1 150                                50 0.5                                      37  280  0.380                                                    77  310                                                           3.3 100    C2 PP(300)THIZ              0.32%                  7%  300                         0.1 125                                50 0.5                                      46  420  0.304                                                    74  273                                                           3.4 107    C3 PP(400)THIZ              0.24%                  6%  450                         0.1 150                                50 2.5                                      154 1250 0.686                                                    69  302                                                           3.6 88    C4 PP(400)THIZ              0.24%                  6%  200                         0.1 100                                50 0.1                                      54  980  0.535                                                    64  209                                                           3.1 98    C5.sup.a       PP(400)THIZ              0.24%                  6%  200                         0.1 150                                40 1.0                                      23  280  0.151                                                    77  345                                                           3.7 76    C6 PP(400)THIZ              0.24%                  6%  400                         0.1 100                                40 1.0                                      53  480  0.262                                                    71  323                                                           3.2 87    C7 PP(400)THIZ              0.24%                  6%  200                         0.1 125                                45 0.4                                      26  470  0.255                                                    74  318                                                           4.0 93    C8.sup.b       PP(300)THIZ              0.50%                  7%  250                         0.5 125                                50 -- 185 1290 1.480                                                    76  300                                                           2.8 107    C9 PP(277)THIZ              0.72%                  13% 200                         0.1 125                                50 1.0                                      57  350  0.574                                                    75  362                                                           2.7 81    C10       PP(277)THIZ              0.72%                  13% 200                         0.1 125                                50 1.9                                      98  600  0.979                                                    72  -- --  --    C11       PP(308)STHI              0.65%                  12% 100                         0.1 250                                40 0.8                                      62  950  1.230                                                    51  285                                                           2.2 74    C12       PP(330)STHI              0.61%                  11% 100                         0.1 250                                40 0.5                                      58  940  1.150                                                    53  302                                                           2.2 98    C13       PP(308)STHI              0.65%                  12% 100                         0.1 400                                40 0.5                                      61  940  1.220                                                    66  325                                                           2.7 109    __________________________________________________________________________     NOTE: unless otherwise noted, 500 mL propylene, 30 min run.     .sup.a 45 min run.     .sup.b Two liter autoclave with 1250 ml propylene.

    ______________________________________    Run           Zirconocene Catalyst Component    ______________________________________    A1            dimethylmethylene bridged                  bis(cyclopentadienyl)                  zirconium dichloride    A2            dimethylsilanylene bridged                  bis(cyclopentadienyl                  zirconium dichloride    A3            bis(benzylcyclopentadienyl)                  zirconium dichloride    A4            dimethylsilanylene bridged                  bis(methylcyclopentadienyl)                  zirconium dichloride    A5            ethylene bridged                  bis(indenyl) zirconium                  dichloride    A6            dimethylsilanylene bridged                  bis(indenyl) zirconium                  dichloride    A7-A9         bis(n-butylcyclopentadienyl)                  zirconium dichloride    A10           bis(n-butyl                  tetrahydroindenyl) zirconium                  dichloride    A11           bis(tetrahydroindenyl)                  zirconium dichloride    A12           ethylene bridged                  bis(tetrahydroindenyl)                  zirconium dichloride    A13           dimethylsilanylene bridged                  bis(tetrahydroindenyl)                  zirconium dichloride    A14           bis(tetrahydroindenyl)                  zirconium diphenyl    A15           bis(tetrahydroindenyl)                  zirconium                  bis(trimethylsilylmethyl)    A16           bis[bis(tetrahydroindenyl)                  zirconium chloride] oxide    B1-B3         bis(n-butylcyclopentadienyl)                  zirconium dichloride    B4-B8         bis(tetrahydroindenyl)                  zirconium dichloride    B9-B12        bis(tetrahydroindenyl)                  zirconium diphenyl    B13           ethylene bridged                  bis(tetrahydroindenyl)                  zirconium dichloride    B14-B17       dimethylsilanylene bridged                  bis(tetrahydroindenyl)                  zirconium dichloride    C1-C10        bis(tetrahydroindenyl)                  zirconium dichloride    C11-C13       dimethylsilanylene bridged                  bis(tetrahydroindenyl)zirconium                  dichloride    ______________________________________

    ______________________________________    Definitions for Tables    ______________________________________    Zirconocene:              formula of the zirconocene component of the              catalyst    Catalyst: PP(nnn)THIZ is a (THI).sub.2 ZrCl.sub.2 containing              catalyst prepolymerized with ethylene to              nnn % of its nonprepolymerized weight, and              PP(nnn)STHI is the same but containing              Me.sub.2 Si(THI).sub.2 ZrCl.sub.2.    Catalyst    Zirc:     wt % zirconocene in the supported or              prepolymerized catalyst    MAO:      wt % methylalumoxane in the supported or              prepolymerized catalyst    mg:       weight of catalyst used in the run    MAO ml:   quantity of methylalumoxane (1 M in              toluene) added as cocatalyst to the liquid              phase of the slurry    25% TEAL ml:              quantity of triethylaluminum (25 wt % in              hexane) used as a scavenger cocatalyst    C.sub.2 psi:              incremental pressure of ethylene, above the              vapor pressure of propylene, used for the              run    T °C.:              reaction temperature    Exotherm °C.:              magnitude of the temperature exotherm              observed upon injection of catalyst    ΔT °C.:              magnitude of the temperature exotherm              observed upon injection of catalyst    Yield g:  weight of polymer, after drying, recovered              from the reaction    Activity  Kg of polymer obtained per gram of    Kg/g-Zr/h:              zirconium per hour of reaction    Activity  Kg of polymer obtained per gram of catalyst    Kg/g-cat/h:              per hour of reaction    C.sub.2 wt %:              weight % ethylene in the polymer product as              per ASTM D3900    M.sub.w 10.sup.3 :              weight average molecular weight of the              product as determined from DRI (in              thousands)    MWD:      molecular weight distribution as expressed              by the ratio of the weight average to              number average molecular weights    ML.sub.1+8, 127° C.:              Mooney viscosity as per ASTM D1646    ______________________________________

I claim:
 1. A process for producing an EPC elastomer in slurrypolymerization, comprising:adding an α-olefin monomer in which an EPCelastomer is substantially insoluble to a reaction vessel in an amountand under pressure sufficient to allow utilization of said α-olefin inliquified form as a polymerization diluent: adding ethylene to saidα-olefin monomer polymerization diluent in an amount sufficient tomaintain a desired ethylene/α-olefin ratio in the liquid phase of thereaction vessel and; adding to the mixture of monomers ametallocene/alumoxane catalyst system wherein the metallocene componentof the catalyst is of the formula: ##STR6## where M is zirconium,titanium, or hafnium; each R¹ independently is a C₁ to C₂₀ linear orbranched alkyl or cyclic alkylene group, R² is a C₁ to C₆ linear,branched or cyclic alkylene, an alkyl substituted silanylene or an alkylsubstituted silaalkylene group, each X independently is a halide,hydride, the oxygen of an oxygen bridged zirconocene dimer, or ahydrocarbyl radical, "b" is 0 or 1, and "y" is an integer of 2, 3, or 4;reacting the mixture of olefin monomers for a time sufficient to permitcopolymerization of said ethylene and α-olefin monomers to an EPCelastomer.
 2. The process of claim 1 wherein M is zirconium and saidzirconocene/alumoxane catalyst system is present on a catalyst supportmaterial.
 3. The process of claim 2 wherein said catalyst supportmaterial is a silica gel and said alumoxane is methylalumoxane.
 4. Theprocess of claim 2 wherein the α-olefin monomer is propylene, 1-buteneor a mixture thereof.
 5. The process of claim 4 wherein "b" is 0 and theR² of the zirconocene component of the catalyst is absent.
 6. Theprocess of claim 4 wherein R² of the zirconocene component of thecatalyst is ethylene.
 7. The process of claim 4 wherein R² of thezirconocene component of the catalyst is dimethylsilanylene.
 8. Theprocess of claim 3 wherein the zirconocene component of the catalyst isof the formula ##STR7## and "z" is an integer from 0 to
 2. 9. Theprocess of claim 8 wherein R² of the zirconocene component of thecatalyst is ethylene.
 10. The process of claim 8 where "b" is 0 and R²of the zirconocene component of the catalyst is absent.
 11. The processof claim 8 wherein R² of the zirconocene component of the catalyst isdimethylsilanylene.
 12. The process of claim 8 wherein the catalyst hasa mole ratio of aluminum to zirconium in the range of 10 to 5,000. 13.The process of claim 9 wherein the α-olefin is propylene, 1-butene or amixture thereof.
 14. The process of claim 10 wherein the α-olefin ispropylene, 1-butene or a mixture thereof.
 15. The process of claim 11wherein the α-olefin is propylene, 1-butene or a mixture thereof. 16.The process of claim 8 wherein the temperature for polymerization is inthe range of 0°-80° C.
 17. A process for producing an ethylene-α-olefinelastomeric copolymer in slurry polymerization, comprising the stepsof:adding an α-olefin monomer to a reaction vessel in an amount andunder a pressure sufficient to allow utilization of said α-olefin in aliquified state as a polymerization diluent; adding ethylene to saidα-olefin polymerization diluent in an amount sufficient to maintain adesired ethylene/α-olefin ratio in the liquid- phase in the reactionvessel, and; adding to the mixture of monomers a supportedmetallocene/alumoxane catalyst which has been prepolymerized withethylene or an α-olefin to a weight increase of at least 50% based onthe total weight of the catalyst and support material wherein thecatalyst support is an alumoxane treated inorganic oxide and themetallocene component of the catalyst is of the formula: ##STR8## whereM is zirconium, titanium, or hafnium; each R¹ independently is a C₁ toC₂₀ linear or branched alkyl or cyclic alkylene group, R² is a C₁ to C₆linear, branched or cyclic alkylene, an alkyl substituted silanylene oran alkyl substituted silaalkylene group, each X independently is ahalide, hydride, the oxygen of an oxygen bridged zirconocene dimer, or ahydrocarbyl radical, "b" is 0 or 1, and "y" is an integer of 2, 3, or 4;reacting the mixture of olefin monomers for a time sufficient to permitcopolymerization of said ethylene and α-olefin monomers to an EPCelastomer.
 18. The process of claim 17 wherein M is zirconium and thezirconocene component of the catalyst is of the formula: ##STR9##wherein each R¹ independently is a linear or branched hydrocarbylradical having from 1 to 20 carbon atoms; "b" is 0 or 1, "z" is aninteger from 0 to 2, the R² bridging group is a linear, branched orcyclic alkylene radical having from one to six carbon atoms an alkylsubstituted silanylene group or an alkyl substituted silaalkylene group,and each "X" independently is alkyl, aryl, hydride, or halide.
 19. Theprocess of claim 18 wherein the catalyst support is silica gel and saidalumoxane is methylalumoxane.
 20. The process of claim 19 wherein "b" is0 and R² of the zirconocene component of the catalyst is absent.
 21. Theprocess of claim 19 wherein R² of the zirconocene component of thecatalyst is ethylene.
 22. The process of claim 19 wherein R² of thezirconocene component of the catalyst is dimethylsilanylene.
 23. Theprocess of claim 20 wherein the α-olefin is propylene, 1-butene or amixture thereof.
 24. The process of claim 21 wherein the α-olefin ispropylene, 1-butene or a mixture thereof.
 25. The process of claim 22wherein the α-olefin is propylene, 1-butene or a mixture thereof. 26.The process of claim 19 wherein the temperature for polymerization is inthe range of 0°-80° C.
 27. A process for producing an EPC elastomercomprising contacting under polymerization conditions ethylene and anα-olefin monomer with a metallocene/alumoxane catalyst system whereinthe metallocene component of the catalyst is of the formula: ##STR10##where M is zirconium, titanium, or hafnium; each R¹ independently is aC₁ to C₂₀ linear or branched alkyl or cyclic alkylene group; R² is a C₁to C₆ linear, branched or cyclic alkylene, an alkyl substitutedsilanylene or an alkyl substituted sillaalkylene group; each Xindependently is a halide, hydride, the oxygen of an oxygen bridgedzirconocene dimer, or a hydrocarbyl radical; "b" is 0 or 1; and "y" isan integer of 2 3, or
 4. 28. The process of claim 27 wherein M iszirconium, said zirconocene/alumoxane catalyst system is present on acatalyst support material, and zirconium metal is present in from about0.02 to about 5.0 weight percent based on total catalyst weight.
 29. Theprocess of claim 28 wherein said catalyst support material is a silicagel and said alumoxane is methylalumoxane.
 30. The process of claim 29wherein the α-olefin monomer is propylene, 1-butene or a mixturethereof.
 31. The process of claim 30 wherein "b" is 0 and the R² of thezirconocene component of the catalyst is absent.
 32. The process ofclaim 30 wherein R² of the zirconocene component of the catalyst isethylene.
 33. The process of claim 30 wherein R² of the zirconocenecomponent of the catalyst is dimethylsilanylene.
 34. The process ofclaim 29 wherein the zirconocene component of the catalyst is of theformula: ##STR11## and "z" is an integer from 0 to
 2. 35. The process ofclaim 34 wherein R² of the zirconocene component of the catalyst isethylene.
 36. The process of claim 34 wherein "b" is 0 and R² of thezirconocene component of the catalyst is absent.
 37. The process ofclaim 34 wherein R² of the zirconocene component of the catalyst isdimethylsilanylene.
 38. The process of claim 27 wherein the catalyst hasa mole ratio of aluminum to metal (M) in the range of 1-200.
 39. Theprocess of claim 38 wherein the catalyst is present on a catalystsupport material.
 40. The process of claim 39 wherein the catalystsupport material is silica.
 41. The process of claim 27, wherein saidprocess is a continuous process.
 42. The process of claim 49, whereinsaid process is a continuous slurry process and a hydrocarbon in whichan EPC elastomer is substantially insoluble is employed in an amount andunder pressure sufficient to allow utilization of said hydrocarbon inliquified form as a polymerization diluent.
 43. The process of claim 42,wherein said hydrocarbon employed as a polymerization diluent is in atleast part the α-olefin monomer.
 44. The process of claim 42, whereinthe α-olefin monomer is the hydrocarbon polymerization diluent.